Talking to RS232C, Pulley belts & Increm. / Absolute

First of all I have to say thanks to everyone on here who's helped these
last few days answering my annoying questions. Since plugging the lathe in
my learning curve has become more than vertical. I can now program the
machine's own controller with simple stuff which is great fun because it
looks really hard to everyone else! `.^)

However, I have a few more questions I'd like to ask and I thought it'd be
easier to ask them all in one post. So here goes:

1.) Pulley belts
The belt that connects my spindle motor to the spindle itself is making a
squeeking, rubbing sound. I've slowed the machine down and it appears to
only squeek, or rub, as certain points of it go passed. I have run the
machine up and down to try and bed the belt in incase it was just a bit
stiff but that's not helped. The pulleys have radial grooves (Why not axial
like stepper pulleys?) and the belt does sit in them. I was worried at first
it may be the chopper wheel rubbing on the tach's sensors but it's not.

2.) RS232C
I got the null modem and plugged the machine in to have a mess around but
with no luck. I've written to the guys at Denford and asked them the details
of the controller such as it's handshake type and that. I have been trying
with WIN CNC 2K. Are there any other programs that would allow to me
communicate with it thru the RS232C? I believe I have it plugged into my
serial comm 1 port for the mouse.

3.) Absolute and Incremental
What do these two mean? It took me a while to work out that if I said:
X= 0
Z= -100
Then,
X= 0
Z= -200
That I'd end up at Z= -300 but there is some funky stuff gong down in
absolute. For instance, if I ask the machine to move the two at the same
time it starts churning away, sometimes asking it to move the X means the Z
ends up moving. I switched it over to incremental and all these problems
went. What's the difference between these two?

Thanks again, I'm off to play around with the screw threading and circular
interplotation buttons, I haven't tried them yet,

A very happy lathin' John Heritage